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Commands such as ALTER USER, ALTER GROUP, ALTER ROLE, GRANT, and the various ALTER OBJECT / OWNER TO, as well as ad-hoc clauses related to roles such as the AUTHORIZATION clause of CREATE SCHEMA, the FOR clause of CREATE USER MAPPING, and the FOR ROLE clause of ALTER DEFAULT PRIVILEGES can now take the keywords CURRENT_USER and SESSION_USER as user specifiers in place of an explicit user name. This commit also fixes some quite ugly handling of special standards- mandated syntax in CREATE USER MAPPING, which in particular would fail to work in presence of a role named "current_user". The special role specifiers PUBLIC and NONE also have more consistent handling now. Also take the opportunity to add location tracking to user specifiers. Authors: Kyotaro Horiguchi. Heavily reworked by Álvaro Herrera. Reviewed by: Rushabh Lathia, Adam Brightwell, Marti Raudsepp.
src/backend/parser/README Parser ====== This directory does more than tokenize and parse SQL queries. It also creates Query structures for the various complex queries that are passed to the optimizer and then executor. parser.c things start here scan.l break query into tokens scansup.c handle escapes in input strings kwlookup.c turn keywords into specific tokens keywords.c table of standard keywords (passed to kwlookup.c) gram.y parse the tokens and produce a "raw" parse tree analyze.c top level of parse analysis for optimizable queries parse_agg.c handle aggregates, like SUM(col1), AVG(col2), ... parse_clause.c handle clauses like WHERE, ORDER BY, GROUP BY, ... parse_coerce.c handle coercing expressions to different data types parse_collate.c assign collation information in completed expressions parse_cte.c handle Common Table Expressions (WITH clauses) parse_expr.c handle expressions like col, col + 3, x = 3 or x = 4 parse_func.c handle functions, table.column and column identifiers parse_node.c create nodes for various structures parse_oper.c handle operators in expressions parse_param.c handle Params (for the cases used in the core backend) parse_relation.c support routines for tables and column handling parse_target.c handle the result list of the query parse_type.c support routines for data type handling parse_utilcmd.c parse analysis for utility commands (done at execution time)